CVE-2026-12633 Out-of-bounds write in IPv6 6LoWPAN Context Option handling via unauthenticated Router Advertisement

The IPv6 neighbor-discovery code in subsys/net/ip/ipv6nbr.c processes the 6LoWPAN Context Option 6CO, RFC 6775 carried inside ICMPv6 Router Advertisements. In handlera6co the 8-bit contextlen field is taken directly from the packet and was never bounded to the RFC maximum of 128. The function...